With the development of LED illumination techniques, more and more people use an LED illumination device as a light source for applications to various environments. As for an illumination device with a fixed light source, the characteristics of light emitted by the light source are generally set, for example, spectral power distribution, color temperature (CCT) and color rendering index (CRI), and so on. However, in many specific application environments such as hotels, malls, or residential buildings, it is often required to adjust the hue of the output light of the illumination device, especially the CCT, to change the lighting atmosphere according to the need or the mood of people, for example, the illumination device emits warm white light when a user spends his leisure time, and emits cool white light when a user studies and works.
In the existing illumination devices, the lens mounted in the illumination device only has an incident surface in a single shape, for receiving incident light emitted from light sources with different colors. These light sources with different colors have different color temperatures, and most of the incident light directly goes through the lens to emit scatteredly, which makes it impossible to deflect the optical path of the light emitted to the lens via the same incident surface in a desired direction, viz. it is impossible to make fine adjustment to the optical path. Thus, the color mixing effect cannot be improved via the lens, the system efficiency of the illumination device mounted with the lens is thereby limited, and more energy consumption is required for light adjustment and light mixing. For example, as shown in FIG. 1, when the illumination device 200 has a first light source in the center and two second light sources on both sides, respectively, first and second incident light respectively emitted from the first and second light sources enters the lens 100 via incident surfaces, as the incident surfaces have the same curved surface profile, it is impossible to make fine adjustment to the optical path of the incident light through the lens, and it is also difficult to mix light by means of the lens. The light emitted through the lens does not have an ideal color, and the obtained light distribution pattern has, for example, merely an elongated shape, rather than an ideal circular shape.